World Water Speed Record Attempt: It's 42 ft long, weighs four tons, has 25,000 horsepower and its creator says it can run on the water at 400mph. A British team has spent 10 years researching and building what they believe will be the world's fastest boat. In early 2009, they hope to put it to the test and break Ken Warby's world water speed record of 317.6 mph.